Arno Martin

Imageless navigation for TKA increases implantation accuracy.

Because we are performing TKAs on heavier, younger patients, greater stress is being put on the implants and is increasing the importance of implantation accuracy. We performed a prospective randomized study to compare the radiographic results and the 3-month clinical outcomes in 100 patients who had TKAs using an imageless navigation system with 100 patients treated using conventional implantation instruments. We measured component alignment by standard radiographs. Clinical outcomes were based on the Insall score, anterior knee pain, feeling of instability, and the step test. The mechanical axis of the limb was within 3° varus/valgus in 92% of the patients who had navigated procedures versus 76% of patients who had conventional surgery. The tibial slope showed a rate of inaccuracy of 3° or less for 98 % of the patients in the navigated TKA group versus 80% of the patients in the conventional group. The surgical time was longer for navigated TKA than for the conventional procedure (88 ± 16 versus 68 ± 18 minutes, respectively). Clinical outcomes and postoperative blood loss were similar in both groups. The navigation system increased implantation accuracy but did not prevent outliers and did not solve the problems associated with identifying and obtaining accurate component rotation.Level of Evidence: Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Two-year outcomes of computed tomography-based and computed tomography free navigation for total knee arthroplasties.

Optimal component position in all planes and well-balanced soft tissues facilitate a good clinical outcome and long-term survival after total knee arthroplasties. We investigated the accuracy of implantation of navigated total knee arthroplasties at 3 months followup and the influence on the clinical outcome at 2 years followup. Forty-four patients (44 procedures) were enrolled in our prospective study. One half of the surgeries were performed using a computed tomography-based navigation system, and half were performed with im-ageless navigation. Outcomes were based on the Insall knee score parameters, anterior knee pain, patient satisfaction, feeling of instability, and step test. The radiographic parameters were the mechanical axis, tibial slope, lateral distal femoral angle, and medial proximal tibial angle. The radio-graphic measurements were similar in both groups (patients within ± 3° inaccuracy range in computed tomography-based/imageless groups; mechanical axis 86%/81%, tibial slope 95%/91%, lateral distal femoral angle 95%/91%, medial proximal tibial angle 91%/95%). The imageless system provided equal radiographic results, but we found improved ligament balancing in the computed tomography free group. The computed tomography-based approach has a good pre-operative planning procedure, but is more expensive and time consuming. Level of Evidence: Therapeutic Study, Level II. See the Guidelines for Authors for a complete description of levels of evidence.

Conventional versus computer-assisted technique for total knee arthroplasty: a minimum of 5-year follow-up of 200 patients in a prospective randomized comparative trial.

In the literature, studies of computer-assisted total knee arthroplasty (TKA) after mid-term period are not conclusive and long-term data are rare. In a prospective, randomized, comparative study 100 conventional TKAs (group REG) were compared with 100 computer-assisted TKAs (group NAV). Minimum follow-up was 5years. No difference in implant failure was found with 1.1% in group NAV versus 4.6% in group REG (P=0.368). Group NAV showed a significantly less mean deviation of mechanical limb axis (P=0.015), more TKAs (90% versus 81% in group REG) were within 3° varus/valgus and a higher tibial slope and lateral distal femoral angle (LDFA) accuracy was found (P≤0.034). Clinical investigational parameters showed no differences (P≥0.058). Insall and HSS score total were also higher in group NAV (P≤0.016).

Implication of femoral stem on performance of articular surface replacement (ASR) XL total hip arthroplasty.

Taper junctions of large diameter metal-on-metal femoral heads and femoral stems were described as metal ion generator due to accelerated wear and corrosion. However, literature about the Articular Surface Replacement (ASR) total hip arthroplasty (THA) invariably deals with stems manufactured by DePuy Orthopedics (Warsaw, IN, USA). Nothing is known whether different stems with common 12/14 mm tapers affect failure rate or ion release. 99 ASR THA (88 patients) implanted with CoxaFit or ARGE Geradschaft stems (K-Implant, Hannover, Germany) were retrospectively analyzed. After a mean follow-up of 3.5 years revision rate was 24.5%, mostly due to adverse reaction to metal debris (ARMD). CT scan revealed component loosening in 10.3% and pseudotumoral lesions in 12.6%. Elevated ion concentrations (>7 μg/l) were found in 38.6%.

Continuous intra-articular local anesthetic drug instillation versus discontinuous sciatic nerve block after total knee arthroplasty

STUDY OBJECTIVE Sciatic nerve block (SNB) is commonly used as adjunct to femoralis nerve block (FNB) to achieve high-quality pain relief after total knee arthroplasty (TKA). However, this combination is associated with considerable muscle weakness, foot drop and surgically related nerve injuries may be masked. The purpose of this study was to assess whether low risk continuous intra-articular anesthetic drug instillation is an adequate alternative to SNB when adding to FNB after TKA. DESIGN Retrospective investigational follow-up study. SETTING University teaching hospital. Interdisciplinary postoperative anesthetic and orthopedic survey. PATIENTS For this investigational analysis, 34 of 50 consecutive patients were available. INTERVENTIONS All patients underwent primary unilateral TKA. Group A (18 patients) received a continuous intra-articular 0.33% ropivacaine (5 mL/h) instillation for the first 48 h postoperatively. In Group B (16 patients) a discontinuous SNB was used. Both groups were treated with a continuous FNB. MEASUREMENTS Main endpoints were mean and maximum postoperative pain intensity levels for both anterior and posterior knee side, amount of postoperative administered opioid drugs, differences in functional outcome or hospital stay and rate of postoperative complications. MAIN RESULTS Group A showed higher pain intensity levels for the posterior knee side (P≤.042). Merely on the second postoperative day there were no differences within either study group. No differences were found regarding anterior knee pain. Group A showed a significant higher postoperative piritramid consumption (P≤.007). Length of hospital stay or postoperative functional outcome was not significant different. Postoperative complications were not related to anesthesia techniques. CONCLUSIONS SNB technique resulted in superior pain relief in comparison to continuous intra-articular local anesthetic drug instillation as adjunct to continuous FNB after TKA.

[Post-traumatic osteoarthritis of the knee: special indication for navigated TKA].

Different studies confirmed the increased radiological implantation accuracy for computer-assisted total knee replacements. There was no study stating a significant influence of the navigation technique for total knee arthroplasties on the early clinical outcomes. In these two case reports we try to show special indications for a navigated total knee replacement to utilize the benefits of a navigation system as efficiently as possible.Case 1 had a femoral neck fracture 3 years ago and was treated with a long femoral gamma nail. The hardware was still retained. Case 2 had a fracture of the femoral diaphysis 31 years ago and showed an extra-articular deformity in the frontal and sagittal planes. Both patients developed osteoarthritis of the ipsilateral knee and were implanted with a total knee prosthesis using a navigation system.In both cases the prosthesis components showed perfect radiological alignment. The clinical outcomes at the 3-month follow-up were very satisfying. In case 1 the femoral nail did not have to be removed, thus decreasing surgery duration by 40-60 min.In both cases, the impossibility of using a femoral intramedullary alignment rod could be compensated for by the navigation system.

Revision of Articular Surface Replacement (ASR) Total Hip Arthroplasty: Correlation of Perioperative Data and Early Post-Revision Outcome Results

The articular surface replacement (ASR) total hip arthroplasty (THA) showed accelerated failure rates due to adverse-reaction to metal debris (ARMD). Literature correlating preoperative with intraoperative revision findings respectively post-revision outcome results are rare. 30 of 99 available ASR THA were revised due to ARMD. Mean post-revision follow-up term was 2.3 years. In part, preoperative data did not correlate with intraoperative revision findings. ARMD was even found in asymptomatic patients with non-elevated ion levels. Postoperative pain and metal ions decreased significantly (P ≤ 0.016). Cobalt decreased faster than chrome. Patients with intraoperative pseudotumors, osteolysis or bilateral THA did not have higher pre- or postoperative ion values (P ≥ 0.053). Females showed higher postoperative chrome levels (P=0.031). One major post-revision complication (femoral nerve palsy) and one re-revision (late onset infection) occurred.

Comparison of two minimally invasive implantation instrument-sets for total knee arthroplasty: Reply to letter by Yasuo Niki

Thank you for your interest in the paper authored by Martin et al. ‘‘Comparison of two minimally invasive implantation instrument-sets for total knee arthroplasty’’ [6]. Dr. Niki is correct, there is a theoretical possible variance in our study because three different surgeons participated in the study. Let me assure you that all three surgeons are well experienced in total knee replacement and extremely familiar with the implanted prosthetic design as well as with the minimal invasive implantation instrument-sets. One of the three surgeons was involved in all analyzed surgeries (surgeon or first assistant). We think that while our study might be criticized because of the variables in question, we stand by our conclusions concerning accuracy of implant positioning. We were not allowed to influence the randomization process. In the future, we will attempt to incorporate preoperative patient characteristics cohort matching. In our opinion, the accuracy of a minimal invasive implantation instrument-set should not be influenced by a preoperative deformity of the mechanical axis with a mean of 9.2 ± 4.6 (19 varus -12 valgus) versus 5.9 ± 3.7 (14 varus -7 valgus) or a body mass index with mean of 30.5 ± 5.3 (21.4–39.1) versus 27.9 ± 3.3 (20.7–35.7). Between the navigated/non-navigated TKAs, no significant demographic or leg deformity differences could be found in each group (Group A ? Group B). In the MIS QuadSparing instrumentation group (Group A), the navigation system had no influence on the implantation accuracy in contrast to Group B where the navigation system could significantly improve the accuracy parameter as we know it from the literature [1, 7]. In fact, it was a disadvantage of the MIS Quad-Sparing instrumentation that an intramedullary nail was mandatory during fixation of the femoral side-cutting jig. Thus, the navigation system could just be used for a verification of the bone cut but not for the definitive positioning of the cutting jig. The intramedullary rod was available with a ‘‘valgus-angle’’ of 3–7 . So you are correct, the benefit of the navigation system was limited because of the implantation instrument design. These limitations have resulted in a decision not to use the MIS Quad-Sparing instrumentation. Through personal communication, I am aware that the instrument designers have stopped using the instrumentation as well. All your key points concerning fixation of the sidecutting jigs firmly to the bone were applied during our study. Nevertheless, we often detected a loosening of the cutting jig even when we left the low-profile intramedullary rod in place until the bone cut of the medial compartment was completed. The bone cuts should be performed in 20–30 of flexion because the collateral ligaments are lax in the latter position. According to the literature [5, 7], we can reach an implantation accuracy of ±3 from the ideal in more than 75% of the knees when standard implantation instruments are used. Even when using minimally invasive instruments with an anterior/posterior cutting direction, implantation accuracies of ±3 were reported in more than 90% of the knees also when using no navigation system [10]. So the reported results in your study [9] (70% vs. 50%) are not acceptable to us. Performing an exact preoperative A. Martin (&) A. von Strempel Department of Orthopedic Surgery, Academic Teaching Hospital Feldkirch, Carinagasse 47, 6800 Feldkirch, Austria e-mail: Arno.Martin@lkhf.at